Motion conversion mechanisms have greatly contributed to mechanical engineering, mechanical industries and other related fields since the Industrial Revolution.
On the other hand, it is also a fact that the designers in those fields have been restricted by the motion characteristics of the conventional motion conversion mechanisms.
In conventional engines, the motion conversion mechanism comprises connecting rods and cranks disposed between pistons and a crankshaft. Such a motion conversion mechanism has the limitations described below.
First, the acceleration of the pistons is very low in the vicinity of the dead points.
Second, the piston velocity or the piston displacement is defined by the angular position of the crank, arbitrary regulation of the motion throughout the whole stroke is impossible.
Third, deviated components of the piston force continuously act on the cylinder wall and toward the center of revolution of the crankshaft, thereby making the movements of the pistons unstable and increasing friction. Because of these limiting features, there are many restrictions in obtaining the optimum motion of the pistons, and accordingly, it is difficult to control the combustion conditions in the working chamber, thereby making it impossible to obtain maximum power and maximum efficiency in an engine.